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I Need IMSAI 8080 Boot Disk For 5 1/4" DS/DD Floppy Disk

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RWoerz

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I have an IMSAI 8080 with the original 8080 cpu board and a Tarbell 1011d floppy disk controller. I think it had 8" floppies but they're long gone. I have a couple DS/DD 5 1/4" floppy drives and it looks like the controller has a connector for 5 1/4" drives. What I don't have is a CP/M boot disk. I built my first 8080 computer in 1975 that ran CP/M but all the brain cell that remember any of that is also long gone. So I need some help. Is there anyone out there that can supply me with a bootable floppy or any image of one. I have a KryoFlux board so I should be able to create a disk from an image.

I guess there is also the question if the Tarbell controller can even talk to a DS/DD drive. Does the boot routine in ROM care what floppy controller is in the machine. Since the controller was working in the machine when it was put away I think it should work.

Thanks for any help I can get.
 
If the big chip in the middle of your controller is a WD1771, you can handle single-density disks only. Note that the boot ROM is configured to boot the 128 byte sector from (0,0,1). By default, it's single-sided, but there's probably enough circuity on the PCB to cobble up a double-sided interface.
 
RWoerz said:
I have an IMSAI 8080 with the original 8080 cpu board and a Tarbell 1011d floppy disk controller. I think it had 8" floppies but they're long gone. I have a couple DS/DD 5 1/4" floppy drives and it looks like the controller has a connector for 5 1/4" drives. What I don't have is a CP/M boot disk. I built my first 8080 computer in 1975 that ran CP/M but all the brain cell that remember any of that is also long gone. So I need some help. Is there anyone out there that can supply me with a bootable floppy or any image of one. I have a KryoFlux board so I should be able to create a disk from an image.

I guess there is also the question if the Tarbell controller can even talk to a DS/DD drive. Does the boot routine in ROM care what floppy controller is in the machine. Since the controller was working in the machine when it was put away I think it should work.

Thanks for any help I can get.
Click to expand...
The Tarbell 1011 was a single-density floppy controller board. It had a very small 128 byte boot loader in ROM, and was designed for use with an 8" single density floppy disk and drive.

8" boot disk images can be found here:

If you no longer own an 8" floppy drive, consider using a Gotek floppy drive emulator (running Flashfloppy firmware) and connect it to your Tarbell controller's 8" floppy drive connector using a 50 pin to 34 pin (8" drive to 5.25" drive) cable adapter.

The Tarbell boot disk loads a CP/M operating system, and CP/M was always customized to run on the hardware installed in the system. I believe the default configuration for Tarbell's boot disk had the console status on port 0, and the data on hardware port 1. If your system has a console board that uses different port numbers and/or requires software configuration before use, you will have to do a lot more work to get your system running.

To provide you with more help, it is essential we know exactly what make/model of other boards are installed in your IMSAI besides the CPU board and the floppy controller. There is no "standard" configuration for an IMSAI, and no "standard" boot disk for an IMSAI.
 
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It should also be mentioned that the 1011 is for 8" disks, which means that the data clock is what we would call "high density". It could be made to work with a 1.2MB 5.25" HD disk or a 1.44M 3.5" drive+disk. But not a "360K" 5.25" drive. Note that this is still using FM encoding.
 
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RWoerz said:
Looks like I may as well go with the CF to IDE card.
Click to expand...
Indeed, bringing up your IMSAI using this Tarbell controller would be a significant (and depending on your level of experience) formidable project.

If the goal is simply to get your IMSAI running, another option you can consider is the "JAIR" 8080-based single board computer. It supports the IMSAI front panel, and allows you to boot and run CP/M from its on-board SD card:

S100 Computers - 8080 CPU Board

S100 Computers
www.s100computers.com
The board is available for sale on eBay from its designer.
 
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Still need some help. Well I bought a Gotek and a 5.25" 34 pin to 8" 50 pin adapter board. I should be able to use my current floppy controller assuming it still works. So I'm still looking for a boot image but for the Goteck. I guess it would same as the one for 8" floppy.
 
The Tarbell card isn't very complicated; loads fhe first sector for you. After that, it's not hard to write your own. Diety knows that it was harder back in the 1970s, where I coded the boot on paper and keyed it in on the front panel.
 
RWoerz said:
Still need some help. Well I bought a Gotek and a 5.25" 34 pin to 8" 50 pin adapter board. I should be able to use my current floppy controller assuming it still works. So I'm still looking for a boot image but for the Goteck. I guess it would same as the one for 8" floppy.
Click to expand...
Your Gotek will be emulating a SSSD floppy disk and drive therefore - yes - you use the same image as for a real 8" floppy disk.

Several images are available at the link I provided previously. You can also find some additional information here:

deramp.com

deramp.com deramp.com
 
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